This explanation
for forgetting has
a biological basis.
Parkin (1993) describes the
making of memories as
'permanent alteration of the brain
substrate in order to represent
some aspect of a past experience'.
The permanent change that
takes place in the brain cells
when memories become fixed
is referred to as consolidation.
An early theory theory about the
biological changes involved in
memory was proposed by Hebb
(1949), who referred to 'cell
assemblies', which were groups
of brain cells, or neurons.
When we receive information
from the senses, these cell
assemblies act to hold the
information long enough for a
permanent memory to be formed.
Hebb thought that the
consolidation and formation
of a permanent memory
took around 30 minutes.
Nowadays, modern
techniques enable us
to see the changes that
take place when new
memories are formed.
Brain cells, or neurons, are
connected to each other at synapses.
At the synapse, chemicals known as
neurotransmitters as passed from one
neuron to another. These chemicals
can either stimulate or inhibit the
activity of neurons. So in any network
of connecting neurons there will be a
pattern of stimulation and inhibition.
Brain research suggests that
the pattern of activity between
connecting neurons forms the
basis for making a memory.
The neurotransmitter acetylcholine has
been identified as very important for the
consolidation process. It follows,
therefore, that interfering with the activity
of acetylcholine could disrupt
consolidation, and that this lack of
consolidation would lead to forgetting.
Research Study:
Drachman and Sahakian
(1979).
Parkin (1993) identified
different steps in the
consolidation process.
The first stage happens
quickly and results in an
'initial fixation' of the memory.
In the second stage, links
are established between
the new memory trace and
our existing memories.
The case of HM, who suffered severe
amnesia following brain surgery,
suggests that consolidation occurs over
quite an extended period of time. HM's
memory for his early life remained
mostly intact, but he did have some
memory loss for event which occurred in
the 2 years before the surgery.
According to Pinel (1993), this appears to go
against Hebb's (1949) idea that the process of
consolidation takes about 30 minutes. The
fact that HM's memory is disrupted for the
2-year period leading up to the surgery
indicates that the process of consolidation
continues for a number of years.
Evaluation.
The explanation is consistent
with what we know about the
nervous system and how the
brain processes information.
The theory links both biological
and psychological approaches
to explaining human behaviour.
There is still no clear
evidence about exactly how
long is required for
consolidation to take place.
In the case of HM, there could
have been other explanations
for his forgetting. In any event
his case was so unusual that we
should not generalise from it to
cases of everyday forgetting.
Most instances of forgetting in real life do
not involve interference with psychoactive
drugs, a blow to the head or brain
surgery. Maybe lack of consolidation
occurs only rarely in real life.